Like everyone I know, my music collection isn't tagged perfectly, so
Rhythmbox analyzes my music folder and recognises the following artists:

Belle and Sebastian
Belle And Sebastian
Belle & Sebastian

This sort of problem could be dealt with very quickly if there were a
right-click context menu action to aggregate the currently selected artists
into one new or existing artist name. Rhythmbox would write tags to all
affected files and update its database and interface to reflect the
corrected and simplified artist list.